Its starting to get cold so one morning I turned my heat on and the air was cold even thought the engine is warmed up. I just drained the coolant and replaced the thermostat and it didnt seem to change at all. Also the dash gauge starts below the lowest line and when it gets warmed up it goes up to the lowest line and stops. It has a 195 degree thermostat fyi. When I set my foot on the gas and let it sit at about 2500 rpm, then heat starts coming out, when I let off, it goes cold again.

 

The blower resistor block went bad, maybe? Thats just the first thing I thought of. Could be something more in depth lol

 

Did you test the thermostat before installing it to make sure it works correctly?

 

I have had this same problem for years with no conclusion on how to fix it. The best thing i can do is pull the heater hoses off the connections at the fire wall and spray some hi pressure water through the heater core and that helps a little. I do this every fall. If you figure out the problem let me know. I have 2 '93 dakotas that both have the same problem.

Matt

 

No I didnt test it. But the old one had the same issue showing lower than accurate readings on the dash. I dunno what's causing that. But what do you use to blow high pressure water into the heater core?

 

i had only cold air come out for a whole summer and had to use a ice scrapper to remove frost on the inside of the truck haha not safe. had my mechanic flush the heater core and heat has been great

 

How much did that cost you?